Add warning scores are floats (#42667)

docs/reference/query-dsl/query_filter_context.asciidoc

@@ -52,12 +52,12 @@ GET /_search
   "query": { <1>
     "bool": { <2>
       "must": [
-        { "match": { "title":   "Search"        }}, <2>
-        { "match": { "content": "Elasticsearch" }}  <2>
+        { "match": { "title":   "Search"        }},
+        { "match": { "content": "Elasticsearch" }}  
       ],
       "filter": [ <3>
-        { "term":  { "status": "published" }}, <4>
-        { "range": { "publish_date": { "gte": "2015-01-01" }}} <4>
+        { "term":  { "status": "published" }}, 
+        { "range": { "publish_date": { "gte": "2015-01-01" }}} 
       ]
     }
   }
@@ -68,11 +68,16 @@ GET /_search
 <2> The `bool` and two `match` clauses are used in query context,
     which means that they are used to score how well each document
     matches.
-<3> The `filter` parameter indicates filter context.
-<4> The `term` and `range` clauses are used in filter context.
-    They will filter out documents which do not match, but they will
+<3> The `filter` parameter indicates filter context. Its `term` and 
+    `range` clauses are used in filter context. They will filter out 
+    documents which do not match, but they will
     not affect the score for matching documents.
 
+WARNING: Scores calculated for queries in query context are represented 
+as single precision floating point numbers; they have only
+24 bits for significand's precision. Score calculations that exceed the
+significand's precision will be converted to floats with loss of precision.
+
 TIP: Use query clauses in query context for conditions which should affect the
 score of matching documents (i.e. how well does the document match), and use
 all other query clauses in filter context.